The Diabetes Control and Complications Trial (DCCT) clearly demonstrated that tight glycemic control profoundly reduces the progression of vascular complications in patients with type 1 diabetes (T1D). In the subsequent Epidemiology of Diabetes Interventions and Complications (EDIC) observational study, both the conventional (CONV) and intensive treatment (INT) DCCT groups were shifted to INT. Surprisingly, the former CONV group continue to develop micro- and macrovascular complications at significantly greater rates than the previous INT group. This concept, called metabolic memory, has been a major enigma in the field of T1D. Recent evidence suggests that epigenetic factors like chromatin histone modifications (PTMs) regulate genes associated with diabetic complications and metabolic memory. However, the role of epigenetic marks like DNA methylation (DNA-me) in human T1D complications progression and metabolic memory is not clear and we propose to address this major gap in knowledge in the current proposal. Based on our recently published data showing alterations in key histone PTMs in sixty patients from the EDIC cohort, as well as new preliminary DNA-me data, our objective is to now explore DNA-me associated mechanisms underlying diabetes complications progression using valuable archived genomic DNA from a bigger cohort of DCCT patients. These samples will be obtained in collaboration with EDIC from their Central Biochemistry laboratory where genomic DNA has been archived from nearly all the DCCT participants at DCCT closeout (1991-1993). In addition, data already generated from our recent study with EDIC cohort patients will also be used for integration with new data generated in this proposal. Four Specific Aims will be evaluated to test the Central Hypothesis that persistent epigenetic changes (DNA-me and histone PTMs) induced by hyperglycemia at key susceptible genome regions during the DCCT can lead to a metabolic memory of the more persistent complications noted during EDIC in the DCCT CONV cohort that was shifted from CONV to INT therapy. The results of these investigations can help establish firmer associations between epigenetics, complications progression and potentially human metabolic memory. This proposal is both timely and significant because human epigenomics is at the forefront of medical research and yet, not much is known in the field of human diabetic complications. These investigations, which use only archived material, can make a significant impact by advancing our understanding of key epigenetic mechanisms underlying the progression of T1D complications despite glycemic control. This, in turn, could determine whether improved early glycemic control can prevent hyperglycemia induced epigenetic changes, and thus lead to newer and more effective therapeutic interventions. Together, these innovative studies address a key scientific gap and clinical need in the field of T1D and its complications that are in line wth the goals of this NIDDK DP3 initiative.